Another problem with conspiracies is that they grow legs. Most Americans are now against immigration in general, even if they may not buy into the more extreme arguments against it.
If the U.S. opened the floodgates and let everyone in from South of the border who wanted to enter, chances are it would jolt the economy in a good way something fierce. But people now believe the lies to enough of a degree that they think letting immigrants in will make their hunt for housing, etc., even harder than it is now.
The directs attention away from real causes of things like high housing prices, such as the takeover of rental markets by private equity firms and mega apartment corporations.
Americans are lazy when it comes to learning about the issues they face.
If they allow Trump back into office, I'm afraid they'll get what they deserve.